Biomedical subjects
Publications and source records attributed to A Villari.
In this paper a new non isothermic method for the determination of the release drug rate constant (k) from a transdermal delivery system is proposed. The new method was applied to transdermal patches Trans-Ver-Sal. The results obtained prove to be able to release salicylic acid of transdermal system and the effectiveness of the new method propose.
The complete pH-rate profile of the hydrolysis reaction of aspirin, requiring many experiments in the past, was obtained by a single variable-parameter kinetic experiment carried out by varying the hydrogen ion concentration. The experiment was carried out spectrophotometrically, reading automatically absorbance, pH, and temperature inside the reaction vessel. The results obtained by the fast processing of the kinetic profile are identical to those obtained under the same conditions but using traditional constant-pH kinetic runs. This method provides the possibility of reducing the amount of time and chemicals usually spent in collecting kinetic data in such mechanistic studies by nearly two orders of magnitude.
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The pseudo-first order rate constant for the hydrolysis of cinnoxicam as a function of temperature was obtained by variable-temperature kinetic experiments. The method used is on a generalization of non-isothermal analysis, and takes advantage of the capabilities of modern data collection and processing systems. A spectrophotometric method under non isothermal conditions was carried out. The results obtained are identical to those obtained under the same conditions by using traditional constant-temperature kinetic runs. This provides the possibility of reducing the amount of time spent and chemicals usually used in collecting kinetic data in mechanistic studies in solution by an order of magnitude.
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Wild, pigmented strains of Serratia marcescens and their non-pigmented mutants were compared on the basis of fatty acid profiles and lipid content. Classic biochemical tests show only minor differences, as well as fatty acid ratio C18:C16. The total amount of lipid synthesized and the saturated/unsaturated fatty acids ratio disclose a sharp total lipid reduction and a high percentage of unsaturated fatty acids in the pigmented strains, placing them in separated clusters compared with the nonpigmented mutants. It is hypothesized that the synthesis of the polyacetate required for the completion of the prodigiosin molecule may result in waste of methyl groups and thus affect the total amount of lipids.
Glycyrrhizin (G) and its aglycone, glycyrrhetic acid (GA) have been prescribed for several therapeutic purposes. However, side effects have pointed out the problem of the toxicity of G. On the contrary, it was recently shown that the pure aqueous liquorice extract (LE), which also contains G, produces reduced adverse effects in rat and human, as compared to pure G, this is likely be related to differences in G bioavailability and the resulting pharmacokinetics of G and GA. Using a sensitive HPLC procedure for the determination of G and GA in rat bile, pharmacokinetics of G and GA in bile have been determined. The results of the analysis showed significantly lower concentrations of G in bile samples from rats treated with LE compared to pure G. Furthermore, LE presented a significant choleretic effect after both oral and i.v. administration, which increases the excretion rate of G. In case of GA, all the concentrations were very low, often below the detection limit. The results prompted us to assess the risk associated with liquorice intake and to determine the daily amount of pure liquorice root extract that can be safely consumed.
Pseudo-first-order rate constants for the hydrolysis of acetylsalicylic acid as a function of temperature have been obtained by variable-temperature kinetic experiments. A method, based on a generalization of non-isothermal analysis, has been used that takes advantage of the capabilities of modern data collection and processing systems. Both spectrophotometric and, for the first time under non-isothermal conditions, fluorometric measurements have been carried out. The results obtained are identical to those obtained under the same conditions but using traditional constant-temperature kinetic runs. This provides the possibility of reducing the amounts of time and chemicals usually spent in collecting kinetic data in mechanistic studies in solution by an order of magnitude.
In 1992-94 we screened 6315 students for coeliac disease (CD) by testing antigliadin antibodies (AGA) as the first-level investigation. We found 28 biopsy-proven coeliac patients who were invited to start the gluten-free diet (GFD). The aim of this study was a clinical and laboratory follow-up in these screening-detected coeliac adolescents. Patients were 17 females and 11 males with a mean age at diagnosis of 12.8 +/- 1 years (range 11-4). Mean follow-up duration time was 23 +/- 7 months (range 9-37). Twenty-three of the 28 screening-detected coeliac patients came to the control visit, 3 refused the follow-up and 2 subjects were not found. Twelve patients (52.2%) stated that they never ate any gluten-containing food, while 11 of them (47.8%) reported occasional transgressions to the diet. GFD acceptance was reported as good (n = 6), moderate (n = 11) or low (n = 6). After starting the GFD, signs of improvement were seen in most patients, such as weight gain, increased height velocity and increased feeling of well-being. AGA (both IgG and IgA classes) and antiendomysium antibodies (AEA) were normal in 19 subjects, 2 cases had IgG-AGA and AEA positivity, 1 patient showed abnormal AGA and AEA levels, while isolated IgA-AGA positivity persisted in 1 case. This study shows that even silent CD cases can clinically benefit from the GFD. The consequences of occasional transgressions to the GFD remain unclear.
This paper deal with the spectroscopic analysis of proteins, i.e., human serum albumin (HSA) and bovine serum albumin (BSA). These two proteins present very similar UV absorption and fluorescence spectra. The UV-spectra of both proteins result from the sum of the absorption spectra of the aromatic amino acid, mainly tryptophan and tyrosine, present in the biological molecules. On the contrary, the fluorescence HSA and BSA spectra are not the sum of the emission fluorescence spectra of tyrosine and tryptophan, but they are mainly constituted by the tryptophan fluorescence with a poor contribution arising from tyrosine. This fact may be due to inter- and intramolecular quenching phenomena. Significant difference were recorder in the life time fluorescence decay of HSA and BSA, which showed tau values of 2.3 and 4.5 nanoseconds, respectively. The time-resolved fluorescence spectroscopy was performed with an experimental apparatus assembled in our laboratories, which is able of measuring the fluorescence decay in the range 2 x 10(-10)-2 x 10(-8) sec.
In this work, a solid-state spectrofluorimetric method for drug assays was developed. In particular, we report the determination of salicylic acid (SA), as a hydrolysis product, in solid pharmaceutical formulations containing acetylsalicylic acid (ASA). Recently, we described a sensitive and accurate fluorescence method that provided, through a mathematical application, the simultaneous determination of ASA and SA. By means of the spectrofluorimetric method reported herein it was possible to carry out the SA determination, without any mathematical calculation and with a sensitivity 100 times that of our previous method. The intra- and inter-day reproducibility of the spectrofluorimetric method, expressed as the relative standard deviation, ranged from 0.1 to 0.3%. The present method requires a fluorescence apparatus with the excitation and detection systems in-line (zero angle). The detection system was not sensitive to the excitation wavelength, but was highly sensitive to emission wavelengths from 350 to 800 nm. The results obtained were compared with those of our previous spectrofluorimetric method, together with those of a high-performance liquid chromatography method and a US Pharmacopeia method. The sensitivity of the method was of the order of 10(-8) g.
We report the simultaneous determination of aspirin and its hydrolysis product, salicylic acid, in solid phase by fluorescence spectrophotometry. Aspirin is often the most labile component in a combination-type analgesic compound. Therefore, its stability is often the initial concern in any formulation-screening program. Preliminary screening of a large number of potential formulations can be arduous, because most current methods of analysis generally consist of several steps: extractions or column separations followed by UV, colorimetric, or gas-liquid chromatographic assays. The method proposed here is quite suited to large numbers of assays because it is not time consuming, it is straightforward, and it is not subject to interference from the substances present in the pharmaceutical formulations. In addition, the method is nondestructive, not dependent on the sampling procedure, and, above all, quite sensitive.
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High-performance liquid chromatographic (HPLC) and diffuse infrared reflectance spectroscopic techniques for qualitative and quantitative analysis of naturally occurring phenolic compounds in Crataegus oxyacantha L. have been applied. (+)-Catechin, (-)-epicatechin and a phenolic acid, the caffeic acid, were investigated in various extractives of Crataegus oxyacantha L. The reversed-phase chromatographic separation was achieved by a combination of isocratic and gradient elution.
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Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.